Various methods and devices have been developed to measure the electrical properties of tissue in an effort to distinguish between cancerous and non-cancerous tissue. For example, U.S. Pat. No. 5,800,350 to Coppleson et al. discloses an apparatus for tissue type recognition. In particular, an apparatus includes a probe configured to contact the tissue and subject the tissue to a plurality of different stimuli such as electrical, light, heat, sound, magnetic and to detect plural physical responses to the stimuli. The apparatus also includes a processor that processes the responses in combination in order to categorize the tissue. The processing occurs in real-time with an indication of the tissue type (e.g. normal, pre-cancerous/cancerous, or unknown) being provided to an operator of the apparatus.
The complex impedance of tissue is generally measured by applying a voltage across at least two electrodes and measuring the current that flows between the electrodes. In order to make accurate measurements these devices employ multiple electrodes (U.S. Pat. No. 5,807,272, U.S. Pat. No. 6,026,323).
These devices are generally large and/or require multiple needles to be inserted into the tissue. In addition, to improve the accuracy of these diagnostic devices multiple sensors are integrated into the probe. For example, U.S. Pat. No. 6,109,270 to Mah et. al. and pending U.S. patent application Ser. No. 09/947,171 to Hular et al. disclose a multimodality instrument for tissue characterization. In order to minimize trauma, what is needed in the art is a new small electrical probe device that provides accurate measurements of the tissue impedance and provides space for additional sensors.